1. Field of Invention
This disclosure relates to a light emitting diode circuit. More particularly, the present invention relates to a white light emitting diode circuit.
2. Description of Related Art
The light emitting diodes (LEDs) are estimated to be four times as efficient as conventional incandescent lights. They are also claimed to be more economically sound than compact fluorescent bulbs that contain harmful mercury and are supposed to last a lot longer than conventional lighting. Therefore, LEDs may become the mainstream of the lighting technology.
Feedback voltage is often used to determine the appropriate voltage or current supplied to the LED channels. Usually, the feedback voltage is from the minimal output voltage of the LED channels, which stands for the critical condition of the LED channels. The module providing the driving voltage/current receives the minimal output voltage as the feedback voltage to determine the operation status of the LED channels and further appropriately adjusts the driving voltage/current supplied to the LED channels.
However, it is hard to detect the minimal output voltage of the LED channels because every channel has different voltage drops across the LED strings. It is even more difficult to select the minimal output voltage from the LED channels as the feedback voltage if there are several LED channels disposed in parallel. Accordingly, a new circuit and a new method are required to correctly choose the minimal output voltage from the LED channels as the feedback voltage when there are several LED channels disposed in parallel.